81665743 has 16 divisors (see below), whose sum is σ = 88704000. Its totient is φ = 74937312.

The previous prime is 81665741. The next prime is 81665761. The reversal of 81665743 is 34756618.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81665743 - 2¹ = 81665741 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81665696 and 81665705.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81665741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 96918 + ... + 97756.

It is an arithmetic number, because the mean of its divisors is an integer number (5544000).

Almost surely, 2^81665743 is an apocalyptic number.

81665743 is a deficient number, since it is larger than the sum of its proper divisors (7038257).

81665743 is a wasteful number, since it uses less digits than its factorization.

81665743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1014.

The product of its digits is 120960, while the sum is 40.

The square root of 81665743 is about 9036.9100360687. The cubic root of 81665743 is about 433.8570302859.

The spelling of 81665743 in words is "eighty-one million, six hundred sixty-five thousand, seven hundred forty-three".